Chewing gums consist of a center which contains the actual gum material and a coating. The coating may comprise different components. The coating serves to protect the gum from influences of the environment i.e. temperature, humidity. The coating consists of different layers of products and includes sucrose, colourants, flavours and other additives the coating also contains polyols such as sorbitol, xylitol and erythritol in so-called sugar-free chewing gums.
When centers are used which contain oil or fat it is advisable to seal in the oil or fat with some layers of arabic gum or another film forming substance. Unless this is done the oil or fat may eventually soak through the final coating resulting in unsightly dark patches.
It has been found that coating of the centers may be difficult to achieve depending on the composition of the center. The coating material does not adhere to the center if the material contains too much oil or fat.
In order to overcome this problem it was found that a precoating was very useful. In general precoatings are applied to the centers in from 5 to 10 layers depending on the composition of the centers and of the precoating material. The idea behind this is that precoating material fills up the pores and forms a thin protective film around the center which adheres much better to the coating material.
Materials which have been found to be suitable as precoating materials are arabic gum, gelatine and tapioca dextrins. Due to its properties arabic gum is often difficult to handle. To solubilise the gum arabic the crude lumps have to be ground and the resulting solution has to be cleared afterwards. This process may take up to 24 hours. A disadvantage of these precoating materials is that at relatively low concentration suspensions of these products already have a high viscosity. With high viscosity suspensions it is difficult to coat a product. This necessitates the use of diluted coating suspension which in turn results in the need to apply more layers of coating which makes the coating process much longer.
Other materials which are used for coating of foodstuffs have been described for example Jokay et al. (Food Technol. 21 1064-1066 (1967)) describe the use of thin boiling hydroxypropyl high amylose (70%) starch as a coating material. High amylose starches are known to be subject to retrogradation. These starches also aid in quick setting and drying of the film.
U.S. Pat. No. 3,870,527 relates to the use granular starch based gums to replace gum arabic in lithographic applications. Although use in food applications is mentioned in general the coating or precoating of oil-containing foodstuffs is not mentioned. U.S. Pat. No. 4,837,314 relates to the preparation of cold water soluble etherified or esterified starch derivatives which are particularly suited for use in wall covering adhesive formulations and as protective colloids in emulsion polymerisation processes.
European patent application EP 547 551 relates to the use of edible films and compositions to obtain such films. The compositions contain starch, gelatin, plasticizer, lipid and water.